The disclosure relates to the field of semiconductor technology, and more particularly to an AlGaN template, a method for preparing the AlGaN template, and a semiconductor device comprising the AlGaN template.
At present, most of GaN-based blue light emitting diodes (LEDs) and GaN-based white LEDs use a sapphire substrate. Since sapphire and GaN materials suffer from lattice mismatch and thermal mismatch problems while there is only a small lattice mismatch between AlN materials and GaN materials and between AlN materials and sapphire substrates, AlN is used as a buffer layer between a GaN layer and a sapphire substrate. Specifically, an AlN buffer layer is first grown on a sapphire substrate to form an AlN template, and then GaN epitaxial growth is performed on the AlN template to form an LED epitaxial wafer.
The lattice constant of the AlN buffer layer is smaller than that of GaN and sapphire. Growing GaN epitaxy on the AlN template leads to greater compressive stress in the subsequent GaN epitaxy. When the quantum well structure of the GaN epitaxial growth is grown, the epitaxial wafer is in a warped state, so that the growth temperature of the quantum well structure is not uniform, and the uniformity of the wavelength of the epitaxial wafer is poor, so that epitaxial wafers cannot be mass-produced with high yield.
FIGS. 1A-1B shows a photoluminescence (PL) wavelength mapping map of an LED epitaxial wafer based on a 4-inch AlN template. As can be seen from FIGS. 1A-1B, the edge wavelength of the epitaxial wafer (point A) is 458 nm, and the center wavelength of the epitaxial (point B) is 468 nm. The wavelength difference between the center and the edge is up to 10 nm, and the standard deviation of the wavelength of the entire epitaxial wafer is 4.18 nm. The qualified epitaxial wafers require a standard deviation of the wavelength of 2 nm. Therefore, the epitaxial wafer does not meet the qualification requirements.